Nowadays, more and more companies and organizations employ the Enterprise Virtual Centrex (EVC) service. These enterprise clients publish one EVC number to the public, and both internal users and external users of the enterprise can enjoy services provided by the EVC. For example, by dialing an access number of the EVC, a calling party can get various services such as manual forwarding, automatic forwarding, voice forwarding, and switchboard outwards calling. Manual forwarding refers to the service provided by an operator, with which calls are forwarded by the operator to a called party after inquiry; automatic forwarding means that the calling party directly dials a normal number of the called party, and the system establishes a connection between the calling party and the called party according to the normal number; voice forwarding is that the calling party speaks out another identifier of the called party, for example a name, via a voice system, and the system finds the number of the called party and establishes a session connection; and EVC outwards calling means that an enterprise member calls an external user of the enterprise through the switchboard, which may reduce communication cost for business.
Different from existing Color RingBack Tone (CRBT) services, the enterprise CRBT service can provide a CRBT customized for all internal users of the enterprise, without affecting personal CRBTs of the internal users, and can be customized according to time periods, departments or enterprises.
Mainly, there are two existing methods for implementing the enterprise CRBT service. FIG. 1 illustrates a flow chart of the first method, in which terminal A refers to a calling terminal, terminal B refers to a called terminal, a soft switching entity (SOFTX)/Service Switching Point (SSP) serving the terminal A is denoted as SOFTX/SSP(a), and an SOFTX/SSP serving the called terminal is denoted as SOFTX/SSP(b). The method generally includes the following steps.
Step 101: Terminal A sends to SOFTX/SSP(a) a call request, including telephone number information of terminal B which has subscribed for the enterprise CRBT service.
Step 102: Upon reception of the call request, SOFTX/SSP(a) sends to a Service Control Point (SCP) in an intelligence network an initial message (IDP), including telephone number information of terminal A and terminal B.
Step 103: The SCP determines that terminal B has subscribed for the enterprise CRBT service based on the telephone number information of terminal B, and sends to SOFTX/SSP(a) a CONNECT message including the telephone number information of terminal B and a routing code for a corresponding CRBT.
Step 104: If SOFTX/SSP(a) receives the CONNECT message and determines that the message also includes a resonant CRBT call identifier, which indicates the use of SSP resonance technology in this method for implementing the enterprise CRBT service, then SOFTX/SSP(a) sends to SOFTX/SSP(b) an Initial Address Message (IAM), including the telephone number information of terminal B requesting for a connection between terminal A and terminal B while blocking a ringback tone from terminal B. SOFTX/SSP(b) returns to SOFTX/SSP(a) an Address Complete Message (ACM) indicating the success of establishing the connection. Then SOFTX/SSP(a) sends to a CRBT Advanced Intelligence Peripheral (AIP) an IAM message including the CRBT routing code and establishes a connection with the CRBT AIP, then the CRBT AIP returns an ACM message to SOFTX/SSP(a), and therefore an enterprise CRBT played by the CRBT AIP can be heard at terminal A.
Step 105: An answer message (ANM) is sent to SOFTX/SSP(b) as soon as terminal B is off-hook.
Step 106: Upon reception of the ANM message, SOFTX/SSP(b) sends to the SCP an IDP message reporting the off-hook event of terminal B.
Step 107: Upon reception of the IDP message, the SCP sends to SOFTX/SSP(a) a release message (REL) instructing SOFTX/SSP(a) to tear down the connection to the CRBT AIP to stop the playing of the enterprise CRBT, meanwhile terminal A and terminal B start to communicate.
In the method illustrated by FIG. 1, different subsystems have to be used to implement the CRBT service and switchboard service; consequently, corresponding data have to be stored in both of the subsystems in order to implement the enterprise CRBT service, which increases data redundancy. In addition, this method is only applicable in a wired communication network.
The second existing method for implementing the enterprise CRBT service is illustrated in FIG. 2, where terminal A also refers to a calling terminal, terminal B also refers to a called terminal, and an SSP/Mobile Switching Center (MSC)/Gateway Mobile Switching Center (GMSC) serving terminal A is denoted as GMSC/MSC/SSP(a), and a GMSC/MSC/SSP serving the called terminal is denoted as GMSC/MSC/SSP(b). The method generally includes the following steps.
Step 201: Terminal A sends to GMSC/MSC/SSP(a) a call request including a telephone number of terminal B which has subscribed for the enterprise CRBT service. If terminal A is a fixed line user or a user of other mobile networks, the GSMC looks up subscription information of terminal B (T-CSI) in a Home Location Register (HLR); and if terminal A is a local user, the MSC looks up the T-CSI information in an HLR.
Step 202: According to the T_CSI information, GMSC/MSC/SSP(a) sends to an SCP, to which terminal B is homed, an IDP message including the telephone number information of terminal A and terminal B.
Step 203: The SCP issues a Request Report Basic call state model Event (RRBE) to GMSC/MSC/SSP(a), instructing GMSC/MSC/SSP(a) to report link connection status in real time.
Step 204: The SCP sends a CONNECT message to GMSC/MSC/SSP(a) to instruct GMSC/MSC/SSP(a) to establish a connection to a CRBT AIP, including the telephone number of terminal B and a CRBT routing code, and a roaming number of terminal B if terminals A and terminal B are terminals in different networks.
Step 205: Upon reception of the CONNECT message, GMSC/MSC/SSP(a) routes the call request to the CRBT AIP, the CRBT AIP furthers connects the call to GMSC/MSC/SSP(b), and finally GMSC/MSC/SSP(b) connects the call to terminal B.
Step 206: The CRBT A IP plays an enterprise CRBT customized by the called number to terminal A while blocking a ringback tone played from terminal B. When terminal B is off-hook, the switchboard CRBT AIP detects the occurrence of the event and stops playing the enterprise CRBT, and terminal A and terminal B can start to communicate. The connection between GMSC/MSC/SSP(a) and the CRBT AIP is interrupted if the communication ends.
In the method illustrated by FIG. 2, as terminal B is called via the CRBT AIP, the trunk link between the CRBT AIP and GMSC/MSC/SSP(a) is still occupied after the session between terminals A and B is enabled. Such a state will last until the communication between terminals A and terminal B ends, which may result in reduplicate links in implementation of the CRBT service, wastes trunk equipments, and thus degrades the parallel processing capability of the color AIP for CRBT service. In addition, during the call, the calling terminal is connected to the called terminal directly through the telephone number of the called terminal; consequently, only users of an enterprise within the same network can join the enterprise CRBT, which may limit terminals used by the users of the enterprise and cannot meet individualized requirements of the users in the enterprise.